In a wireless communication system, user capacity has been generally limited by signal interference between users within a cell. In recent years, as a solution for overcoming this intra-cell interference problem, a method using an orthogonal code has been proposed.
A method employing an orthogonal code refers to a method in which each user within a cell codes his data using different code resources having orthogonality and transmits the data to a base station, thus preventing interference between users within a cell.
However, there is a problem in that the number of users, which can be accommodated within a single cell, is limited by the number of orthogonal codes that can be generated because the number of orthogonal codes that can be made to have the sequence of a limited length is limited.
This problem may be solved using a method of assigning quasi-orthogonal codes to excess users when the number of users within a cell exceeds the number of orthogonal codes that can be generated. However, as described above, the method of using the quasi-orthogonal codes partially does not become an appropriate solution when the activity of a channel is low. In case where a user equipment is connected to a base station, but the ratio of the time taken to use a channel for data transmission is less, there is a low probability that channels of user equipments using orthogonal codes can be activated at the same time. User equipments transmit data at the same time using quasi-orthogonal codes in which a complete orthogonality is not maintained. Thus, not only complete orthogonal code resources are used inefficiently, but also an effect of prohibiting intra-cell interference may be degraded.
IEEE (Institute of Electrical and Electronics Engineers) 802.16 standard provides technologies and protocols for supporting broadband wireless access. IEEE 802.16-2004/Cor1 of the IEEE 802.16-2004 standard, which was authorized in 2004, was completed in the form of “corrigendum” in order to modify bugs and error in 2005. The IEEE 802.16-2004 standard adopts a solution in which uplink wireless communication resources, used by a user equipment for transmission of data to a base station, are scheduled grossly in order to prevent intra-cell interference.
However, a significant signaling overhead is required in order for the base station to grossly schedule wireless communication resources for each user equipment. This is because a considerable amount of signaling is needed in order to allocate and release resources for each user within a cell. In particular, when user distributions within a cell are frequently changed or there are a lot of users to be accommodated within a single cell, a signaling cycle is too long, which may make its implementation substantially difficult.